预应力混凝土连续梁腹板裂缝成因分析

Cause Analysis of Web Cracks in Prestressed Concrete Continuous Beam

为研究某预应力混凝土连续箱梁在施工及运营阶段腹板斜向裂缝的产生原因,在混凝土塑性损伤理论基础上建立空间模型,对施工阶段钢束张拉工况进行模拟。研究结果表明:钢束张拉时,混凝土强度不足导致腹板产生裂缝;腹板主拉应力矢量方向基本与预应力钢束走向垂直,主拉应力大致随距锚固端距离增加而减小,采用塑性损伤模型计算结果与现场检测情况基本吻合;拟采取的竖向预应力加固方法可有效降低腹板开裂风险。

In order to study the causes of the slant web cracks that appear in the construction and operation stage of a prestressed concrete continuous box girder extending in the direction of prestressed reinforcement, a spatial model is established based on the plastic damage theory of concrete to simulate the tension condition of steel bundles in the construction stage. The results are shown as the following. When the steel bundle is tensioned, the insufficient strength of concrete leads to web cracks. The direction of the main tension stress vector of the web is basically perpendicular to the direction of the prestressed steel bundle. The main tension stress decreases roughly with the increase of anchor end distance. The calculated results by using plastic damage model are basically consistent with the on-site test results. The proposed vertical prestressed reinforcement method can effectively reduce the risk of the web cracking.